Fix CVE-2017-2636

3 files changed, 323 insertions, 5 deletions

diff --git a/.SRCINFO b/.SRCINFO
index c4b625a7349d..901fe64bf70d 100644
--- a/.SRCINFO
+++ b/.SRCINFO
@@ -1,6 +1,6 @@
 pkgbase = linux-bfq
 	pkgver = 4.10.2
-	pkgrel = 1
+	pkgrel = 2
 	url = http://algo.ing.unimo.it
 	arch = i686
 	arch = x86_64
@@ -22,6 +22,7 @@ pkgbase = linux-bfq
 	source = config.x86_64
 	source = 99-linux.hook
 	source = linux.preset
+	source = 0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch
 	validpgpkeys = ABAF11C65A2970B130ABE3C479BE3E4300411886
 	validpgpkeys = 647F28654894E3BD457199BE38DBBDC86092693E
 	sha512sums = c3690125a8402df638095bd98a613fcf1a257b81de7611c84711d315cd11e2634ab4636302b3742aedf1e3ba9ce0fea53fe8c7d48e37865d8ee5db3565220d90
@@ -37,6 +38,7 @@ pkgbase = linux-bfq
 	sha512sums = 6afb164bc7a38fea08a49c70690afafb209d1245588e1ecf57998926f5b43fe85d39a1ab1a133900b82bc1d3d97538330bf5c646b62e782653d69b6139d72200
 	sha512sums = d6faa67f3ef40052152254ae43fee031365d0b1524aa0718b659eb75afc21a3f79ea8d62d66ea311a800109bed545bc8f79e8752319cd378eef2cbd3a09aba22
 	sha512sums = 2dc6b0ba8f7dbf19d2446c5c5f1823587de89f4e28e9595937dd51a87755099656f2acec50e3e2546ea633ad1bfd1c722e0c2b91eef1d609103d8abdc0a7cbaf
+	sha512sums = 397fc751697cc4e2ceb7e6d854f5e7fc115ed8511df406ffe5d8f80afeec385ba64cd28c4666bb206612fdcd7a578b60ca6ff125c2138c615aee6135d86b0197
 
 pkgname = linux-bfq
 	pkgdesc = Linux Kernel and modules with the BFQ scheduler.
diff --git a/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch b/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch
new file mode 100644
index 000000000000..0c13c98674dc
--- /dev/null
+++ b/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch
@@ -0,0 +1,311 @@
+>From 1dea7a8061ad9212f4464464a80d0dcd477eceab Mon Sep 17 00:00:00 2001
+From: Alexander Popov <alex.popov () linux com>
+Date: Tue, 28 Feb 2017 19:28:54 +0300
+Subject: [PATCH 1/1] tty: n_hdlc: get rid of racy n_hdlc.tbuf
+
+Currently N_HDLC line discipline uses a self-made singly linked list for
+data buffers and has n_hdlc.tbuf pointer for buffer retransmitting after
+an error.
+
+The commit be10eb7589337e5defbe214dae038a53dd21add8
+("tty: n_hdlc add buffer flushing") introduced racy access to n_hdlc.tbuf.
+After tx error concurrent flush_tx_queue() and n_hdlc_send_frames() can put
+one data buffer to tx_free_buf_list twice. That causes double free in
+n_hdlc_release().
+
+Let's use standard kernel linked list and get rid of n_hdlc.tbuf:
+in case of tx error put current data buffer after the head of tx_buf_list.
+
+Signed-off-by: Alexander Popov <alex.popov () linux com>
+---
+ drivers/tty/n_hdlc.c | 132 +++++++++++++++++++++++++++------------------------
+ 1 file changed, 69 insertions(+), 63 deletions(-)
+
+diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
+index eb27883..728c824 100644
+--- a/drivers/tty/n_hdlc.c
++++ b/drivers/tty/n_hdlc.c
+@@ -114,7 +114,7 @@
+ #define DEFAULT_TX_BUF_COUNT 3
+ 
+ struct n_hdlc_buf {
+-	struct n_hdlc_buf *link;
++	struct list_head  list_item;
+ 	int		  count;
+ 	char		  buf[1];
+ };
+@@ -122,8 +122,7 @@ struct n_hdlc_buf {
+ #define	N_HDLC_BUF_SIZE	(sizeof(struct n_hdlc_buf) + maxframe)
+ 
+ struct n_hdlc_buf_list {
+-	struct n_hdlc_buf *head;
+-	struct n_hdlc_buf *tail;
++	struct list_head  list;
+ 	int		  count;
+ 	spinlock_t	  spinlock;
+ };
+@@ -136,7 +135,6 @@ struct n_hdlc_buf_list {
+  * @backup_tty - TTY to use if tty gets closed
+  * @tbusy - reentrancy flag for tx wakeup code
+  * @woke_up - FIXME: describe this field
+- * @tbuf - currently transmitting tx buffer
+  * @tx_buf_list - list of pending transmit frame buffers
+  * @rx_buf_list - list of received frame buffers
+  * @tx_free_buf_list - list unused transmit frame buffers
+@@ -149,7 +147,6 @@ struct n_hdlc {
+ 	struct tty_struct	*backup_tty;
+ 	int			tbusy;
+ 	int			woke_up;
+-	struct n_hdlc_buf	*tbuf;
+ 	struct n_hdlc_buf_list	tx_buf_list;
+ 	struct n_hdlc_buf_list	rx_buf_list;
+ 	struct n_hdlc_buf_list	tx_free_buf_list;
+@@ -159,6 +156,8 @@ struct n_hdlc {
+ /*
+  * HDLC buffer list manipulation functions
+  */
++static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
++						struct n_hdlc_buf *buf);
+ static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
+ 			   struct n_hdlc_buf *buf);
+ static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
+@@ -208,16 +207,9 @@ static void flush_tx_queue(struct tty_struct *tty)
+ {
+ 	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
+ 	struct n_hdlc_buf *buf;
+-	unsigned long flags;
+ 
+ 	while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
+ 		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
+- 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
+-	if (n_hdlc->tbuf) {
+-		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
+-		n_hdlc->tbuf = NULL;
+-	}
+-	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
+ }
+ 
+ static struct tty_ldisc_ops n_hdlc_ldisc = {
+@@ -283,7 +275,6 @@ static void n_hdlc_release(struct n_hdlc *n_hdlc)
+ 		} else
+ 			break;
+ 	}
+-	kfree(n_hdlc->tbuf);
+ 	kfree(n_hdlc);
+ 	
+ }	/* end of n_hdlc_release() */
+@@ -402,13 +393,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
+ 	n_hdlc->woke_up = 0;
+ 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
+ 
+-	/* get current transmit buffer or get new transmit */
+-	/* buffer from list of pending transmit buffers */
+-		
+-	tbuf = n_hdlc->tbuf;
+-	if (!tbuf)
+-		tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
+-		
++	tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
+ 	while (tbuf) {
+ 		if (debuglevel >= DEBUG_LEVEL_INFO)	
+ 			printk("%s(%d)sending frame %p, count=%d\n",
+@@ -420,7 +405,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
+ 
+ 		/* rollback was possible and has been done */
+ 		if (actual == -ERESTARTSYS) {
+-			n_hdlc->tbuf = tbuf;
++			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
+ 			break;
+ 		}
+ 		/* if transmit error, throw frame away by */
+@@ -435,10 +420,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
+ 					
+ 			/* free current transmit buffer */
+ 			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
+-			
+-			/* this tx buffer is done */
+-			n_hdlc->tbuf = NULL;
+-			
++
+ 			/* wait up sleeping writers */
+ 			wake_up_interruptible(&tty->write_wait);
+ 	
+@@ -448,10 +430,12 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
+ 			if (debuglevel >= DEBUG_LEVEL_INFO)	
+ 				printk("%s(%d)frame %p pending\n",
+ 					__FILE__,__LINE__,tbuf);
+-					
+-			/* buffer not accepted by driver */
+-			/* set this buffer as pending buffer */
+-			n_hdlc->tbuf = tbuf;
++
++			/*
++			 * the buffer was not accepted by driver,
++			 * return it back into tx queue
++			 */
++			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
+ 			break;
+ 		}
+ 	}
+@@ -749,7 +733,8 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
+ 	int error = 0;
+ 	int count;
+ 	unsigned long flags;
+-	
++	struct n_hdlc_buf *buf = NULL;
++
+ 	if (debuglevel >= DEBUG_LEVEL_INFO)	
+ 		printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
+ 			__FILE__,__LINE__,cmd);
+@@ -763,8 +748,10 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
+ 		/* report count of read data available */
+ 		/* in next available frame (if any) */
+ 		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
+-		if (n_hdlc->rx_buf_list.head)
+-			count = n_hdlc->rx_buf_list.head->count;
++		buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
++						struct n_hdlc_buf, list_item);
++		if (buf)
++			count = buf->count;
+ 		else
+ 			count = 0;
+ 		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
+@@ -776,8 +763,10 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
+ 		count = tty_chars_in_buffer(tty);
+ 		/* add size of next output frame in queue */
+ 		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
+-		if (n_hdlc->tx_buf_list.head)
+-			count += n_hdlc->tx_buf_list.head->count;
++		buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
++						struct n_hdlc_buf, list_item);
++		if (buf)
++			count += buf->count;
+ 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
+ 		error = put_user(count, (int __user *)arg);
+ 		break;
+@@ -825,14 +814,14 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
+ 		poll_wait(filp, &tty->write_wait, wait);
+ 
+ 		/* set bits for operations that won't block */
+-		if (n_hdlc->rx_buf_list.head)
++		if (!list_empty(&n_hdlc->rx_buf_list.list))
+ 			mask |= POLLIN | POLLRDNORM;	/* readable */
+ 		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+ 			mask |= POLLHUP;
+ 		if (tty_hung_up_p(filp))
+ 			mask |= POLLHUP;
+ 		if (!tty_is_writelocked(tty) &&
+-				n_hdlc->tx_free_buf_list.head)
++				!list_empty(&n_hdlc->tx_free_buf_list.list))
+ 			mask |= POLLOUT | POLLWRNORM;	/* writable */
+ 	}
+ 	return mask;
+@@ -856,7 +845,12 @@ static struct n_hdlc *n_hdlc_alloc(void)
+ 	spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
+ 	spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
+ 	spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
+-	
++
++	INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
++	INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
++	INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
++	INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
++
+ 	/* allocate free rx buffer list */
+ 	for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
+ 		buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
+@@ -884,53 +878,65 @@ static struct n_hdlc *n_hdlc_alloc(void)
+ }	/* end of n_hdlc_alloc() */
+ 
+ /**
++ * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
++ * @buf_list - pointer to the buffer list
++ * @buf - pointer to the buffer
++ */
++static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
++						struct n_hdlc_buf *buf)
++{
++	unsigned long flags;
++
++	spin_lock_irqsave(&buf_list->spinlock, flags);
++
++	list_add(&buf->list_item, &buf_list->list);
++	buf_list->count++;
++
++	spin_unlock_irqrestore(&buf_list->spinlock, flags);
++}
++
++/**
+  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
+- * @list - pointer to buffer list
++ * @buf_list - pointer to buffer list
+  * @buf	- pointer to buffer
+  */
+-static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
++static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
+ 			   struct n_hdlc_buf *buf)
+ {
+ 	unsigned long flags;
+-	spin_lock_irqsave(&list->spinlock,flags);
+-	
+-	buf->link=NULL;
+-	if (list->tail)
+-		list->tail->link = buf;
+-	else
+-		list->head = buf;
+-	list->tail = buf;
+-	(list->count)++;
+-	
+-	spin_unlock_irqrestore(&list->spinlock,flags);
+-	
++
++	spin_lock_irqsave(&buf_list->spinlock, flags);
++
++	list_add_tail(&buf->list_item, &buf_list->list);
++	buf_list->count++;
++
++	spin_unlock_irqrestore(&buf_list->spinlock, flags);
+ }	/* end of n_hdlc_buf_put() */
+ 
+ /**
+  * n_hdlc_buf_get - remove and return an HDLC buffer from list
+- * @list - pointer to HDLC buffer list
++ * @buf_list - pointer to HDLC buffer list
+  * 
+  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
+  * list.
+  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
+  */
+-static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
++static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
+ {
+ 	unsigned long flags;
+ 	struct n_hdlc_buf *buf;
+-	spin_lock_irqsave(&list->spinlock,flags);
+-	
+-	buf = list->head;
++
++	spin_lock_irqsave(&buf_list->spinlock, flags);
++
++	buf = list_first_entry_or_null(&buf_list->list,
++						struct n_hdlc_buf, list_item);
+ 	if (buf) {
+-		list->head = buf->link;
+-		(list->count)--;
++		list_del(&buf->list_item);
++		buf_list->count--;
+ 	}
+-	if (!list->head)
+-		list->tail = NULL;
+-	
+-	spin_unlock_irqrestore(&list->spinlock,flags);
++
++	spin_unlock_irqrestore(&buf_list->spinlock, flags);
+ 	return buf;
+-	
+ }	/* end of n_hdlc_buf_get() */
+ 
+ static char hdlc_banner[] __initdata =
+-- 
+2.7.4
+
diff --git a/PKGBUILD b/PKGBUILD
index e585a1d49e7f..cdfa3d3af214 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -52,7 +52,7 @@ pkgbase=linux-bfq
 # pkgname=('linux-bfq' 'linux-bfq-headers' 'linux-bfq-docs')
 _srcname=linux-4.10
 pkgver=4.10.2
-pkgrel=1
+pkgrel=2
 arch=('i686' 'x86_64')
 url="http://algo.ing.unimo.it"
 license=('GPL2')
@@ -80,7 +80,7 @@ source=("http://www.kernel.org/pub/linux/kernel/v4.x/${_srcname}.tar.xz"
          # standard config files for mkinitcpio ramdisk
         'linux.preset'
         # patches from https://github.com/linusw/linux-bfq/commits/bfq-v8
-        )
+        '0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch')
 
 _kernelname=${pkgbase#linux} 
 
@@ -89,7 +89,11 @@ prepare() {
 
     ### Add upstream patch
         msg "Add upstream patch"
-        patch -Np1 -i "${srcdir}/patch-${pkgver}" 
+        patch -Np1 -i "${srcdir}/patch-${pkgver}"
+    
+    ### Patch for CVE-2017-2636
+        msg "Fix CVE-2017-2636"
+        patch -p1 -i "${srcdir}/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch"
 
     ### Patch source with BFQ
         msg "Patching source with BFQ patches"
@@ -435,7 +439,8 @@ sha512sums=('c3690125a8402df638095bd98a613fcf1a257b81de7611c84711d315cd11e2634ab
             '1f0a8695b7c106d7946d67eaa8ebcf4e0bccd2cae01b0cd5621af04aa42f7e9a1b379764fb9bd9917f85ff719ec28e081eeb7c143a682f6d179e2bd1d7d15d7e'
             '6afb164bc7a38fea08a49c70690afafb209d1245588e1ecf57998926f5b43fe85d39a1ab1a133900b82bc1d3d97538330bf5c646b62e782653d69b6139d72200'
             'd6faa67f3ef40052152254ae43fee031365d0b1524aa0718b659eb75afc21a3f79ea8d62d66ea311a800109bed545bc8f79e8752319cd378eef2cbd3a09aba22'
-            '2dc6b0ba8f7dbf19d2446c5c5f1823587de89f4e28e9595937dd51a87755099656f2acec50e3e2546ea633ad1bfd1c722e0c2b91eef1d609103d8abdc0a7cbaf')
+            '2dc6b0ba8f7dbf19d2446c5c5f1823587de89f4e28e9595937dd51a87755099656f2acec50e3e2546ea633ad1bfd1c722e0c2b91eef1d609103d8abdc0a7cbaf'
+            '397fc751697cc4e2ceb7e6d854f5e7fc115ed8511df406ffe5d8f80afeec385ba64cd28c4666bb206612fdcd7a578b60ca6ff125c2138c615aee6135d86b0197')
             
 validpgpkeys=(
               'ABAF11C65A2970B130ABE3C479BE3E4300411886' # Linus Torvalds